Wallum And Kwongan: A Very Australian Paradise
Heathland is a general term for a gardenesque plant community found in parts of Australia where conditions are too tough for forest. In NSW, heathland is associated with sandstone, while Queensland’s Wallum heath (named after the Wallum Banksia, Banksia aemula) occurs on coastal sand. Kwongan is Western Australia’s version of heathland. Kwongan also occurs on various sands, sometimes with laterite. The name Kwongan comes from the Noongar people, its traditional owners.
Wherever it grows, Australian heathland brims with sophisticated, unique, easy care, waterwise, colourful plants. Many can be grown at home. In these sun-bathed landscapes, many plant species have evolved to produce prolific quantities of pollen and nectar. This feast attracts a host of insects, mammals and birds which pollinate flowers and disperse seed. At breakfast time, heathland is surprisingly noisy.
The main horticultural difference between east and west coast heathland is the east coast receives summer rain and experiences winter drought, while kwongan has evolved alongside winter rain and summer drought.
Soils are extraordinarily impoverished, even by Australian standards, and plants have evolved various methods of keeping well nourished. Bushfires liberate nutrients in ash beds, seed beds for the next generation of plants. Legumes, like wattles (Acacia spp.) and sheoaks (Casuarina spp.), use nitrogen fixing bacteria to gain extra nutrients, which insectivorous plants, like sundews (Drosera spp.) and the Albany Pitcher plant (Cephalotus follicularis) supplement their diet by capturing animals. Plant parasites (like Cassytha spp.) and semi-parasitic plants (like mistletoes, Amyema spp.) abound. Plants in the Proteaceae family, like Banksia spp., have evolved roots that are super-efficient at extracting phosphorous from the depleted soils. Microscopic mycorrhizal fungi abound, forming intimate bonds with root systems which effectively extends their root system, creating mutually beneficial relationships which help nourish and protect their host plants against drought and disease.
Wherever heathland grows, it contains a diversity of beautiful and fascinating plants, many with distinctive forms unseen elsewhere on Earth, like grass trees (Xanthorrhoea spp.) and the Southern Cross (Xanthosia spp.). The quintessential Australian genus of trees, Eucalyptus, has evolved into low-growing woodland or multi-stemmed ‘mallee’ equipped with fire-proof underground lignotubers.
Heathland is effectively bonsai bushland, and its plants are suited to growing in small spaces, containers – or a glasshouse. In 1982 this London gardener spent most of a six month botanical expedition studying and documenting kwongan, the supreme version of heathland. I exported 450 species, the finest examples, for Kew Gardens to display in what was then called the Australian House.
My expedition followed spring, exploring from the ancient stromatolites of world heritage listed Hamelin Pool near Carnarvon (a personal Mecca), south to the awe-inspiring karri forests of the Walpole-Nornalup National Park, and inland to the expansive eucalypt woodlands of the semi-arid goldfields.
I sought plants which had never before been grown in Europe. I kept detailed written and photographic records, plus two sets of herbarium specimens of each plant collected, one set each for the West Australian and Kew herbaria.
Heathland is fantastic for plant hunting because many plants are bushes and perennials. It is especially rich in plants from the Proteaceae and Myrtaceae families, plants that have co-evolved with the mammals, birds, bees and butterflies that pollinate and disperse their seed. Stingless bees evolved short tongues to perfectly fit the short, cup-shaped , nectar-rich flowers of the Myrtaceae. Heathland honey tastes magnificent, I encourage Australians to try Western Australian banksia honey at least once.
Kwongan is best suited to a dry temperate climate, thriving on 400mm annual rainfall. Often it contains either the most diverse examples of an Australian plant genus, or their most curious examples, and sometimes both. Kwongan’s Banksia, Darwinia, Conospermum, Calothamnus, Dryandra (now merged into Banksia), Synaphea and Verticordia are Australia’s showiest.
Wallum heathland plants cope better with warm, humid summers, so they tend to be easier to cultivate in a glasshouse. Kew Gardens grows some of these species. It is vital, though, that glasshouses are well ventilated. Fans are useful in calm, humid conditions. Plants require freely draining soil, and grow best in raised beds or pots. When watering is necessary, water them at the root in the morning, keeping foliage dry.
In London, I grew heathland plants in terracotta pots, using equal parts of hydroponic aggregate (clay balls, which function like laterite) and coarse horticultural sand (sold there as ‘sharp sand’). To strengthen their growth during the long, gloomy British winters, I used a X-ray lamp.
Periodic bushfire stimulates renewal, like pruning in a home garden. Home gardeners can stimulate grass trees to grow by periodic defoliation. Burning grass trees is unnecessary – pruning initiates a flush of new growth is the same way fire does in the wild. Following summer fire and winter rain, carpets of white flannel flowers (Actinotus spp.) paper daisies and orchids carpet the charred, blackened bushland with flowers.
Kwongan is filled with intricate detail, subtle foliage hues of blue-grey and grey-green copses of wandoo, blackbutt, dwarf cypress, evergreen shrubberies and ground-hugging perennials, like Leschenaultia and lambswool (Lachnostachys eriobotrya). Dunna Dunna, Lawrencia helmsii, the weirdest hibiscus on Earth (which thrives around the edge of alkaline gypsum pans), makes the rush-like restios, tuberous sundews and the semi-parasitic Choretrum, Exocarpus and Spirogardnera (cousins of sandalwood) seem conventional.
Low lying areas gather winter rain, and this extra moisture creates ‘mini-gardens’ filled with glistening enamel orchids, quillworts, trigger plants, comb ferns and, a personal favourite, midget styleworts (Levenhookia). I’ve never botanised so much on my knees!
No species exists in isolation. Plants flower in succession, and each week the kaleidoscope of spring flower colour changes. Australia has 2,000 known species of bee, more than any other continent, because they have evolved alongside the ancient Myrtaceae. Native pomegranate (Balaustion), Baeckia, Eremaea, Regelia and Scholtzia, found in kwongan, produce shallow, cup-like, nectar-filled flowers typical of Myrtaceae, a design that suits our short-tongued bees.
Kwongan remnants occur from Kalbarri through the wheatbelt to Cape Lesueur. I encourage everyone to experience one kwongan spring in their life. Listen to the birdsong at dawn to get an idea of how noisy and industrious heathland nature was when its range hadn’t been diminished by settlement.
My three picks would be autumn in Noosa National Park (Qld), and spring at North Head in the Sydney Harbour National Park, and the Alexander Morrison National Park in Western Australia. Named in honour of WA’s first government botanist, the Alexander Morrison National Park’s remnant 8,500 hectare of kwongan is, in my opinion, simply the most magical garden on Earth.
If you’re interested in growing plants of Wallum Heathland, start by checking out the Coolum Community Nursery, Ph: (07) 5473 9322.
7th May 2016